1. Field of the Invention
The present invention relates to a magnetic recording reproducing apparatus, and more particularly, relates to a tracking system which performs automatic tracking by dividing one track into a plurality of minute blocks, and an automatic tracking method.
2. Discussion of Related Art
A video cassette recorder (VCR) is an apparatus recording video signals on magnetic tape, and has a deck part connected to an electrical part. The standard of the tape and the standard of the recorded signals are strictly provided for compatibility between different VCRs. Especially, the standard of the track linearity is used for the compatibility of VCRs. The width of track for high density recording becomes gradually narrow and determining the optimum tracking point is very important. Thus, as a tape is inserted into a deck, the VCR performs automatic tracking. The user may select either manual or autocontrol, as desired. The autocontrol uses the envelope of a regenerative signal. That is, according to the automatic tracking, the optimum tracking point is automatically determined and maintained as the tape is inserted into the VCR.
The overall flowchart of the automatic tracking is shown in FIG. 1.
As the tape is input to the VCR (Step 101), it goes to a regenerating state (Step 102), and offsetting of the VCR head is performed (Step 103). The output RF signal is filtrated to digitalize the envelope signal (Step 104. The tracking is controlled with a digital value converted in the Step 104, thus finding a tracking value (Step 105). If the tracking value obtained in the Step 105 is not a proper value, it goes to the Step 103 and performs the above procedure. If the proper tracking value is obtained in the Step 105 (Step 106), the track offsetting stops and the tracking value obtained in the Step 105 is maintained.
FIG. 2 is a block diagram of the automatic tracking system using such an envelope. A signal processing part 27 produces a synchronous signal (or Vref) by using input data and applies it to a servo part (26), and servo part 26 rotates a drum and a capstan motor. The data applied to signal processing part 27 is converted to be suitable for tape recording, and is provided to the head through a recording amplifier 23 thereby being recorded on the track of the tape. The drum servo of servo part 26 controls a drum motor so that the drum motor""s rotating phase is synchronized to the normally-recorded video signal""s phase in the recording mode. A capstan servo controls the capstan motor to the number of the capstan motor""s rotation, thereby maintaining the traveling speed of the tape constantly, and recording the signal on the tape by exact pitch. A control signal is recorded on the control track, and the location of the control signal is indicative of that of the recorded signal during reproduction. That is, since there is the standard of a distance between the location of the control signal and the video track, the rotating head traces the track on the basis of the control signal like when recording, and reproduces the recorded signal. One control signal is recorded with respect to two video tracks. Two video heads are attached to a rotating head drum, and two video heads are physically offset from each other (12) in opposite directions (azimuth scanning). A single control is made with respect to one rotating motion of the rotating drum so that a video track recorded by a channel-1 head is traced by the channel-1 head.
Accordingly, servo part 26 rotates the drum and the capstan motor in response to the synchronous signal (or Vref) during reproduction, and a signal produced from the head is amplified by amplifier 23 and is produced to signal processing part 27. Signal processing part 27 receives the amplified signal and restores the same to data, thus producing it to a monitor. The drum servo of servo part 26 controls the number of rotations of the drum motor constantly during reproduction to obtain a regenerative signal without time shaft variation. The capstan servo controls the capstan motor so that the video head exactly traces the track, thus obtaining a regenerative signal of a maximum level. Envelope detecting part 24 detects an envelope signal from the RF signal produced by amplifier 23, and tracking control part 25 digitalizes the envelope signal detected by envelope detecting part 24 to obtain tracking data, and transmits the data to servo part 26.
FIG. 3 is a detailed block diagram of tracking control part 25 of FIG. 2, and an analog/digital (A/D) converter 31 converts the envelope signal Env into a digital signal according to an A/D sampling clock, as shown in FIG. 4b. A summing part 32 sums the envelope signal, digitalized by A/D converter 31, in the unit of a head switching pulse H/SW, as shown in FIG. 4a. The sum area of summing part 32 indicates a single tracking section, a half period of the head switching pulse, as shown in FIG. 4c. Therefore, summing part 32 adds one to several A/D values to one track.
Storing part 33 stores the summed data in an address produced from a tracking controller 35, e.g. an address corresponding to a track offset value. Whenever tracking controller 35 changes a tracking value, e.g. an offset value, the value added by summing part 32 is stored in storing part 33. Storing part 33 stores sum data for each track, as shown in FIG. 5. The horizontal axis of FIG. 5 corresponds to values obtained by offsetting the head when reproducing the track, made during recording. FIG. 6 depicts a tracking offsetting method, and A and B and C correspond to zero and left in offsetting. Track center detecting part 34 obtains a center of the track by the use of data for each track stored in storing part 33. The center of the track may be obtained either by finding the form of a peak curve and obtaining its maximum value, or by obtaining a middle of a value more than a fixed value. Track center detecting part 34 obtains a track center value by the use of one of the above methods, and produces the track center data to tracking controller 35. Tracking controller 35 produces the tracking data to servo part 26, thus performing tracking.
As described above, according to the conventional automatic tracking method, the overall values A/D converted by tracks are summed to process it as one data, and the center of the track is obtained with an average of the overall values. There is no problem of finding the center of the overall signals of the track, and this method cannot cope with deterioration of the linearity of the track or a change in the track. As shown in FIG. 7a, the trace of the recording track in set A has a linearity problem in an upward direction, due to mechanical problems, worn-out tapes, etc., and the trace of the track in set B has a linearity problem in a downward direction, as shown in FIG. 7b. In this occasion, according to the conventional art, the trace of the head exactly overlaps the recording track, as shown in FIG. 7c. However, there are linearity problems as shown in FIGS. 7a and 7b, and an output of the head is depicted in FIG. 7d. If the dotted line of FIG. 7d is a restorable minimum signal level, the data cannot be restored under that level.
Since the narrower the width of the track is, the more the problem becomes serious, recording is made by shuffling data for correcting errors during recording digital data, and when a predetermined part of the track is not restored due to the difference of signal levels, the overall screen is broken.
Accordingly, the present invention is directed to an automatic tracking system and an automatic tracking method that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an automatic tracking system and an automatic tracking method whereby a track is processed as one block to find a one-track center value, and at the same time, the track is divided into a plurality of minute blocks to find a track center value by blocks, thus a finding a new track center value by using the one-track center value and track center values for the respective blocks.
Another object of the present invention is to provide an automatic tracking system and an automatic tracking method whereby a track is divided into a plurality of minute blocks to find a track center value for each block, thus obtaining a new track center value by using that center value.
Still another object of the present invention is to provide an automatic tracking system and an automatic tracking method whereby a track is divided into a plurality of minute blocks to find a track center value for each block, and a mean of the leftmost value and the rightmost value of track center values for the respective values is set as a new track center value.
Still another object of the present invention is to provide an automatic tracking system and an automatic tracking method whereby a track is divided into a plurality of minute blocks and sum data for each block is multiplied by a corresponding weighted value and added to find a new track center value.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention discloses an automatic tracking system including an analog/digital converter converting an envelope signal detected during reproduction into a digital signal; a first track center detecting circuit processing a track as a block, summing and storing data of the analog/digital converter by a head switching pulse, and finding a track center value; a part track center detecting circuit dividing a track into a plurality of minute blocks, summing and storing digital data corresponding to the minute blocks, distributed from the analog/digital converter, in each minute block, and finding a track center value for each minute block; a final track center detecting part finding a new track center value by using track center values output from the first track center detecting circuit and the part track center detecting circuit; and a tracking controller producing an address corresponding to a track offset value when storing sum data in the first track center detecting circuit and the part track detecting circuit, and receiving the track center value from the final track center detecting part and producing that value to a servo part for tracking.
According to another aspect of the present invention, an automatic tracking system includes an analog/digital converter converting an envelope signal detected during reproduction into a digital signal; a part track center detecting circuit dividing a track into a plurality of minute blocks, summing and storing digital data corresponding to the minute blocks, distributed from the analog/digital converter, in each minute block, and finding a track center value for each minute block; a final track center detecting part finding a new track center value by using track center values output from the part track center detecting circuit; and a tracking controller producing an address corresponding to a track offset value when storing sum data in the part track center detecting circuit, and receiving the track center value from the final track center detecting part and producing that value to a servo part for tracking.
According to still another aspect of the present invention, an automatic tracking system includes an analog/digital converter converting an envelope signal detected during reproduction into a digital signal; a part track center detecting circuit dividing a track into a plurality of minute blocks, summing and storing digital data each corresponding to the minute blocks, distributed from the analog/digital converter, in each minute block, and finding a track center value for each minute block; a final track center detecting part determining a new track center value as a mean of the leftmost value and the rightmost value of track center values produced from a plurality of blocks of the part track center detecting circuit; and a tracking controller producing an address corresponding to a track offset value when storing sum data in the part track center detecting circuit, and receiving the final track center value from the final track center detecting part and producing that value to a servo part for tracking.
According to still another aspect of the present invention, an automatic tracking system includes an analog/digital converter converting an envelope signal detected during reproduction into a digital signal; a summing controller dividing a track into a plurality of minute blocks, and distributing digital data of the analog/digital converter to each minute block; a plurality of summing means summing digital data distributed by the summing controller; weighted value means multiplying sum data S1 to Sn, produced from a plurality of that summing means, by respective weighted values a1 to an and adding       (                  ∑                  k          =          1                n            ⁢                        a          n                xc3x97                  S          n                      )    ;
storing means storing sum data produced from the weighted value means; track center detecting means finding a track center value by the use of data stored in the storing means; and a tracking controller producing an address corresponding to a track offset value to the storing means when storing sum data, and receiving the final track center value from the track center detecting means and producing that value to a servo part for tracking.
According to still another aspect of the present invention, a method of performing automatic tracking by converting an envelope signal, detected during reproduction, into a digital signal, includes a first step of summing and storing the envelope signal by a head switching pulse by processing a track as one block, and finding a track center value; a second step of dividing the track into a plurality of minute blocks, summing and storing the digital envelope signal corresponding to each block in each block, and finding a track center value for each minute block; a third step of finding a new track center value by using track center values output in the first and second steps; and a fourth step of producing an address corresponding to a track offset value when storing sum data in the first and second steps, and receiving the final track center value from the third step for tracking.
According to still another aspect of the present invention, a method of performing automatic tracking by converting an envelope signal, detected during reproduction, into a digital signal, includes a first step of dividing the track into a plurality of minute blocks, summing and storing the digital envelope signal corresponding to each block in each block, and finding a track center value for each minute block; a second step of finding a new track center value by using track center values output in the first step; and a third step of producing an address corresponding to a track offset value when storing sum data in the first step, and receiving a final track center value from the second step for tracking.
According to still another aspect of the present invention, a method of performing automatic tracking by converting an envelope signal, detected during reproduction, into a digital signal, includes a first step of dividing the track into a plurality of minute blocks, summing and storing the digital envelope signal corresponding to each block in each block, and finding a track center value for each minute block; a second step of setting as a new track center value a mean of the leftmost value and rightmost value of track center values output from a plurality of the blocks in the first step; and a third step of producing an address corresponding to a track offset value when storing sum data in the first step, and receiving a final track center value from the second step for tracking.
According to still another aspect of the present invention, a method of performing automatic tracking by converting an envelope signal, detected during reproduction, into a digital signal, includes a first step of dividing a track into a plurality of minute blocks, and distributing the digital envelope signal, corresponding to each minute block, to each minute block; a second step of summing the digital envelope signal applied from the first step by the blocks; a third step of multiplying sum data S1 to Sn, produced from a plurality of that summing means, by respective weighted values a1 to an and adding       (                  ∑                  k          =          1                n            ⁢                        a          n                xc3x97                  S          n                      )    ;
a fourth step of storing sum data produced from the third step; a fifth step of finding a track center value by the use of data stored in the storing means; and a sixth step of producing an address corresponding to a track offset value when storing sum data in fourth step, and receiving the track center value from the fourth step and controlling the tracking.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
(Option: In another aspect, the present invention provides . . . )